The present invention applies to the rolling of an aircraft on the ground, in particular an airplane, civil or military, for transporting passengers or merchandise (freight), or else a drone (pilotless aircraft). It relates, more particularly, to the generation of a ground trajectory, which is such that the aircraft can be guided, manually or automatically, along this trajectory on an airport domain such as an aerodrome or an airport.
Within the framework of the present invention, the following meanings are implied:                “rolling on the ground” implies any type of possible rolling of an aircraft, such as rolling on a landing runway in the course of the landing and takeoff phases, or rolling on trafficways or on maneuvering areas, in particular;        “ground trajectory” implies the path followed by the aircraft on the airport domain, including in particular the takeoff and landing runways, the trafficways or taxiways, the turn-around areas, the waiting zones, the stop bars, the stopping positions (stand), the maneuvering areas, and the parking areas; and        “automatic guidance” implies the action of a device forming an integral part of the aircraft and capable of ensuring, partially or totally, that is to say without aid or with the partial aid of a human, the driving of an aircraft on the ground.        
Currently, the (human) pilot controls the lateral movements of the aircraft on the ground with the aid of manual piloting facilities (for example a steering wheel allowing the orientation of the wheel of the front landing gear or a direction rudder bar), along a ground trajectory. These facilities make it possible to control actuators capable of influencing the lateral movements of the aircraft, in particular by way of the orientation of the wheel of the front landing gear (and optionally the orientation of the rear gear), of the rudder of the fin, and of the asymmetric use of the brakes and engines.
The ground trajectory is generally provided to the pilot, for example by way of radiocommunication means or some other standard means such as a digital data transmission link, by an air traffic controller or a ground controller, but it can also, in certain cases, be chosen freely by the pilot.
The trajectory is defined in the form of a succession of elements of the airport domain, and indicates a path making it possible to attain, from one point or region of the airport domain, another point or region of said domain.
Any portion of the domain, whether or not designated by a name, and identified as a distinct and delimited part of the domain, is called an element of the airport domain. An element may optionally overlap one or more others. The takeoff and landing runways, the trafficways or taxiways, the turn-around areas, the waiting zones, the stop bars, the stopping positions (stand), the maneuvering areas and the parking areas are in particular designated as elements.
Knowing the ground trajectory to be followed, the pilot acts on the piloting facilities, so as to control the movements of the aircraft on the ground (the longitudinal speed and the lateral displacements of the aircraft). He does so also in order to follow the trajectory in such a way that all the parts of the aircraft in contact with the ground (the wheels of the front and rear gear) remain permanently on the pavement designed for aircraft rolling. For most airports accommodating civil or military transport airplanes, the term “ground” implies the parts covered with tarmac and designed for this purpose. The pilot's objective is therefore to manage a trajectory so that none of the parts of the aircraft in contact with the ground lies at a given moment on a portion of the airport domain that is not designed for the rolling of the aircraft, in particular portions covered with grass, earth or sand, or portions designed solely for the rolling of lighter vehicles (cars, trucks).
Currently, the pilot has only a map (paper or displayed by computer by an appropriate viewing system in the cockpit) and instructions from the air/ground traffic control describing the trajectory to be followed, so as to guide the aircraft manually from one point to another of the airport domain.
Consequently, in the absence of a representation of the trajectory to be followed utilizable by the computerized systems of the aircraft:                the trajectory tracking lateral guidance cannot be carried out automatically by a device of the aircraft;        the pilot cannot have a visual representation of the trajectory (for example on a display system of the aircraft) which would enable it to aid him to guide the aircraft manually following the lateral axis; and        this guidance presents a very significant workload.        